Objective

1. Objective • Finish with VOCs • Prepare for the field measurements on Friday

2. VOCs in Buildings • Sources • Fate • Effects • Measurement

3. Volatile Organic Compounds (VOCs) VOC • What is a VOC? • Organic = C, H • “affinity for gas phase”, “significant” evaporation rate • Tb < 260 oC • Thousands (reduce list to 50 to 100) • What is TVOC?

4. Categories • Odor-causing • Irritating • SBS – fatigue, eyes, headaches, upper resp., etc • Other – skin irritation, asthma, MCS • Toxic/Hazardous • Carcinogen • Teratogen • Neurotoxin, etc. • Reactive • Generally w/ ozone

5. Representative Examples • Benzene • Toluene • Ethylbenzene • Xylenes (all isomers) • Trimethylbenzenes (all isomers) • Dichlorobenzenes (not all isomers created equal) • Tetrachloroethene (PERC) • Chloroform (a THM) • 4-Phenylcyclohexene (4-PCH) • Styrene • Terpenes (limonene, pinene, etc.) • Formaldehyde (HCHO) – often not classified as a VOC BTEX

6. Relative Exposure to VOCs Exposure (I/O) = 3 x 18 x 0.4 = 22 indoor contribution > 95% (most volatile HAPs, etc.)

7. Some Important Sources • Building materials and furnishing(wood, adhesives, gyp board) • Flooring materials(carpet, vinyl flooring, wood) • Architectural coatings(paints, varnishes, waxes, etc.) • Consumer products(cleaners, detergents, fresheners, personal, etc.) • Combustion sources (ETS, candles, gas stoves, space heaters) • Electronics (computers, photocopiers, printers, TVs/VCRs) • Heating of particulate matter • Soil vapor intrusion • Drinking water • Mold (MVOCs) • People

8. Measurement Issues • Objective(s) • Required detection limits • (Real-time) vs. (collect and analyze) • Non-specific vs. species specific (speciated) • Grab versus integrated • Interferences • Preservation requirements • Quality assurance requirements • EPA/OSHA/NIOSH methods exist? • Cost/Budget Measurement Method

9. Sample Collection Methods • Real-time (field) measurement/analysis • generally = sensor (mostly FID, PID) • some = separation (w/ GC) + sensor • Also – colorimetric tubes (general: MDL > 1 ppm) • Collect for analysis • whole-volume samplers (canisters, bags) • concentration samplers (sorbents, SPME) • either case = preservation and analysis in laboratory

10. Canisters • Whole volume • Grab versus integrated • EPA Methods TO-14 / 15 • Benefits • Inert/impermeable • Experience • Multiple analyses • Drawbacks • bulky • cleaning • Scratch • Ozone / Sample stability 1 – 15 L http://www.skcinc.com 400 mL

11. Tedlar Bags • Whole volume • Tedlar = polyvinylfluoride • Pump to collect (unlike cans) • Issues: • Benefits: • inert / impervious (like cans) • repeat samples (like cans) • lighter than cans • lower initial cost than cans • Drawbacks • not as reuseable as cans • tearing • cleaning • stability with some compounds http://www.essvial.com/products/airsample.html 0.5 – 100 L

12. Sorbent Sampling • VOC adsorbs to solid adsorbent • Passive sampling • Similar to ozone badge • Integrated sample over 24 hours, etc. • Indoor, personal, outdoor • Active Sampling • Pump through packed tube • Collect mass over known volume • C = m/V • Short-term vs. integrated • More control, but more difficult http://www.aerotechpk.com/ http://www.sisweb.com/index/referenc/resin10.htm

13. Sorbent Tubes • EPA Method • Various sorbents can be used • Note VOC types/ranges • Some issues • Method detection limit, precision, accuracy • Sample preservation • Breakthrough volume • Artifact formation (especially via ozone) • Sorbent pre-conditioning / breakdown over time • Use of multi-sorbent beds • Focus on Tenax-TA

14. Tenax-TA • 2,6-diphenylene oxide polymer resin (porous) • Specific area = 35 m2/g • Pore size = 200 nm (average) • Density = 0.25 g/cm3 • Various mesh sizes (e.g., 60/80) • Low affinity for water (good for high RH) • Non-polar VOCs (Tb > 100 oC); polar (Tb > 150 oC) • Artifacts w/ O3: benzaldehyde, phenol, acetophenone

15. Gas Chromatography (GC) • Goal = separate compounds • Use capillary column • Properties of column • Properties of chemical • Thermal program of GC oven • Temporal passage to a detector • analyze “peaks” • analyze molecular fragments (MS)

16. Gas Chromatography (GC) http://www.chromatography-online.org/GC/Modern-GC/rs2.html

17. Figure 5: Chromatogram of Tenax-sampling in a show case (sample volume 1l) - iaq.dk/iap/iaq2003/posters/hahn5.gif Blue slides = www.sisweb.com/art/referenc/aap54

18. GC Issues • Type of injection? • Need to cryofocus? • Type of column? • Type of detector? • If MS, model of detection • Temperature programs • Instrument calibration / response

19. Detectors • Flame ionization detector (FID) • Photoionization detector (PID) • Electron capture detector (ECD) • Mass spectrometer (MS) • These are primary detectors for VOCs in indoor air • Specific uses vary considerably Non-specific or speciated (w/ GC) w/ speciated (w/ GC)

20. Flame Ionization Detectors (FID) • Relatively simple system  • Ions formed – migrate to plate • Generate current • Detection – typical to pg/s • Benefits • Rugged, low cost, workhorse • Linear response over wide range • Insensitive to H2O, CO2, SO2, CO, NOx .. • Drawbacks • No identification • Lower response if not simple HC • Destructive www.chem.agilent.com

21. Photoionization Detectors (PID) • UV light ionizes VOCs --- R + hv  R+ + e- • Collected by electrodes = current • VOCs with different ionization potentials • Benefits • Simple to use • Sample non-destructive (relatively) • Drawbacks • No identification • Highly variable responses • Not all VOCs detected • Lamp burnout / contamination http://www.chemistry.adelaide.edu.au/external/soc-rel/content/pid.htm

22. Electron Capture Detectors (ECD) • Low energy Beta emitter = 63Ni • e- attracted to positively charged electrode (anode) • Molecules in sample absorb e- and reduce current • effective: halogens, nitrogen-containing • Benefits • 10-1,000 x more sensitive than FID • femtogram/s ----- ppt levels • Drawbacks • More limited linear range than FID • Radiological safety requirements • O2 contamination issues • Response strong function of T, P, flowrate http://www.chemistry.adelaide.edu.au/external/soc-rel/content/ecd.htm

23. Mass Spectrometer (MS) • Bombard molecules w/ intense electron source • Generate positive ion fragments • Use fragment fingerprint to identify molecule • Quantify amount of fragments to determine mass • Most common MS = quadrupole

24. Quadrupole MS • Electron source • Four rods (electromagnets) • Applied Voltage • DC/AC components • Voltages = fn(time) • Affects trajectory • Selective M/Z to detector http://www.chemistry.adelaide.edu.au/external/soc-rel/content/quadrupo.htm

25. Total Ion Chromatogram (TIC) linalool limonene Mondello et al.,J. of Chromatography A, 1067: 235-243 (2005)

26. Summary • VOCs important in indoor environments • Many types of VOCs • Different properties • Different effects • Different sample collection and analysis protocols • Sampling and analysis protocols NOT TRIVIAL • Many types of collection methods • Many types of analysis methods / including detectors • A lot of issues involved w/ sample/analysis decisions • A lot can go wrong (difficult business) • Cumbersome and costly -------- but really important

27. Field trip • Friday afternoon • 10800 Pecan Park Boulevard Suite 210. Austin, TX 78750 • Measurement of • Primarily IAQ parameters • …… • Prepare on Thursday • Distribute duties • Equipment assembly • Packing and check out • ….